Mitsubishi Ecodan Error and Fault Codes Guide

Mitsubishi Ecodan heat pumps are well-known for their energy efficiency and reliability, making them a popular choice of heat pump in the UK. However, like any advanced heating solution, they can encounter issues from time to time, which are indicated by specific error or fault codes. If you are reading this article then you are likely already the proud owner of an Ecodan, but you might find our review of the Ecodan interesting if you would like a different opinion on the choice of unit.

In this guide, we’ll walk you through the most common Mitsubishi Ecodan fault codes, what each one means, and give you some step-by-step troubleshooting advice. Whether you're dealing with a water circulation issue, thermistor failure, or communication error, this article will help you quickly identify the problem. You will note that the resolution is not always straightforward, so some of you might have the experience and knowhow to resolve some of the issues yourself, while in other cases it might be best to seek professional help.

What Are Mitsubishi Ecodan Error Messages?

Mitsubishi Ecodan heat pumps use diagnostic error codes to indicate faults and issues with the unit or system. These codes are displayed on the controller panel, helping homeowners and technicians pinpoint the root cause of the issues quickly and efficiently.

Some fault codes can be resolved with simple troubleshooting, while others may require professional servicing.

Common Mitsubishi Ecodan Fault Codes Explained

Here are some of the most frequently encountered Mitsubishi Ecodan fault codes, their meanings, and suggested actions:

F3 - Low Pressure Switch Failure: Check the connection on the board and verify the continuity of the switch.

F5 - High Pressure Switch Failure: Inspect the connection on the board and ensure proper switch operation.

L3 - Circulation Water Temperature Overheat Protection: Check for water leakage, strainer blockage, and ensure the circulation pump is functioning correctly.

L9 - Low Primary Circuit Flow Rate Detected: Inspect for water leakage, strainer blockage, and replace the flow switch if necessary.

U1 - High Pressure Fault: Check water flow rates and ensure no blockages.

U6 - Inverter/Compressor Overcurrent: Perform diagnostic tests on the inverter and compressor.

E0 - Transmitting Error (PAR-W21): Verify and correct refrigerant address settings on SW1.

E6 - Indoor/Outdoor Communication Error: Ensure proper power-up sequence and inspect communication lines.

For a full list of fault codes, meanings, and actions, refer to the detailed table below.